Arsenic in water: bigger cancer threat.

Drinking arsenic-contaminated water constitutes a "far more serious" toxic threat than previously believed, according to Joseph P. Brown, a toxicologist with California's Environmental Protection Agency in Berkeley. Indeed, a new risk assessment by his agency indicates that lifetime consumption of drinking water with levels of arsenic at the current federal limit -- 50 parts per billion (ppb) -- presents a one-in 100 risk of cancer. As environment threats go, he says, "It ranks right up there with radon and secondhand tobacco smoke."

Present throughout Earth's crust, arsenic contaminates groundwater around the world. The U.S. EPA considers its current standard - not originally based on cancer risk -- to correspond to a skin-cancer risk of about 2.5 in 1,000.

Since that limit was issued in 1976, however, researchers in Taipei have correlated cancer mortality in much of Taiwan with arsenic measured in the 83,656 wells serving those individuals. Typically consuming water bearing 150 to 800 parts per billion (ppb) of the contaminant, this population "is almost a laboratory for studying the epidemiology of arsenic," Brown maintains. And the high levels of other cancers associated with arsenic in that study -- malignancies of the lung, liver, kidney, bladder, prostate and other internal sites -- now indicate that the current 50-ppb U.S. standard "is out of line," Brown contends.

On the basis of an analysis of the data from Taiwan and elsewhere by researchers at the University of California, Berkeley, Brown's office has recommended that California's Department of Health Services lower its 50-ppb drinking-water standard and establish an even lower regulatory goal of 2 parts per trillion arsenic. Brown says the lower level corresponds to an overall cancer risk of roughly one in 1 million.